Plasma or serum separation membrane and filter apparatus including the plasma or serum separation membrane

ABSTRACT

A Plasma or serum separation membrane that enables omitting centrifugal separation, is free from hemolysis attributed to destruction of red blood cells and realizes easy and rapid separation of plasma or serum from blood; and a filter apparatus including the plasma or serum separation membrane. In particular, a plasma or serum separation membrane being a membrane for separation of plasma or serum from blood and having a void ratio of 30% or below; and a filter apparatus comprising a filter member capable of attaining movement of plasma swifter than movement of blood cells and a plasma or serum separation membrane connected in series with a rear side of the filter member.

FIELD OF THE INVENTION

The present invention relates to plasma or serum separating membranesfor use in separation of plasma or serum components in blood containingcorpuscles, and more specifically, to a plasma or serum separatingmembrane and a filter apparatus enabling separation of plasma or serumcomponents without causing breakage of erythrocytes.

BACKGROUND ART

Conventionally, a variety of separating membranes have been proposed forremoving corpuscles from blood to obtain plasma or serum required forlaboratory tests.

For example, Japanese Examined Patent Publication No. 2-23831 (1990)discloses a method of colleting plasma from blood using a hollow fiberhaving fine pores of 0.05 to 1 μm in diameter, a porosity of outersurface of not more than 40%, and a porosity of inner surface of notless than 60%.

Japanese Examined Patent publication No. 6-64054 (1994) proposes amethod of separating plasma or serum through a fiber layer having a meandiameter of 0.2 to 5.0 μm and a density of 0.1 to 0.5 g/cm³.

On the other hand, Japanese Unexamined Patent Publication No. 11-285607(1999) discloses a separation method which utilizes difference inmovement speed between corpuscles and plasma or serum components througha polymeric microfiber assembly or a porous polymer. In this method, ahydrophilic polymer is immobilized on a surface of fiber, thehydrophilic polymer swells after separation of plasma or serum, thefilter is clogged, and thereby filtration is automatically stopped.

However, the method disclosed in Japanese Examined Patent PublicationNo. 2-23831 (1990) had an economic problem because high cost is requiredto produce a disposable product due to the hollow fiber.

The method of Japanese Examined Patent Publication No. 6-64054 enablesseparation of plasma or serum, however the filtering speed is stillunsatisfactory. Application of pressure to improve the filtering speedcould sometimes cause breakage of corpuscles, hemolysis, andcontamination of separated plasma or serum with leaking erythrocytes.Additionally, in the blood in which fibrin or the like precipitates,hemolysis was more likely to occur since clogging was more likely tooccur during the separation process.

In the method of Japanese Unexamined Patent Publication JP-A 11-285607(1999), since the filtering speed changes between bloods of differenthematocrits and viscosities, it was impossible to securely stop thefiltration at the point when filtration of plasma or serum completed.

DISCLOSURE OF THE INVENTION

In consideration of the above circumstances of the conventional arts, itis an object of the present invention to provide a plasma or serumseparating membrane enabling reliable and rapid separation of plasma orserum components from blood without causing breakage of erythrocytes,and to provide a filter apparatus using the plasma or serum separatingmembrane.

As a result of diligent research for separation of plasma or serumcomponents from corpuscles in blood, the inventors of the presentapplication found that plasma or serum components can be separated fromcorpuscles without causing hemolysis by using a separation membranehaving pores of specific constitution and accomplished the presentinvention.

A plasma or serum separating membrane of the present invention isintended to separate plasma or serum from blood, and is characterized byhaving a porosity of not more than 30%.

In another specific aspect of the plasma or serum separating membrane ofthe present invention, a plurality of through holes are provided so asto penetrate from one side to the other side of the membrane.

In a more specific aspect of the present invention, diameters of thethrough holes fall within the range of 0.05 to 2.0 μm.

In still another specific aspect of the plasma or serum separatingmembrane of the present invention, mean surface roughness of themembrane is not more than 100 nm.

In a further specific aspect of the plasma or serum separating membraneof the present invention, the plasma or serum separating membrane isused as a corpuscle blocking membrane for preventing contamination bycorpuscles.

A filter apparatus of the present invention comprises a first filtermember through which plasma can move faster than corpuscles, and aplasma or serum separating membrane according to the present invention,serially connected in subsequent stage with the first filter member.

In this description, the expression “serially connected” refers to notonly the case where the objects are directly connected but also the casewhere other member intervenes the objects.

In a specific aspect of the filter apparatus of the present invention,the filter member serves as a first filter member, the plasma or serumseparating membrane serves as a second filter member, and a third filtermember made of fiber having a mean fiber diameter of not less than 3.0μm and a bulk density of not more than 0.3 g/cm³ is provided inprecedent stage of the first filter member.

In another specific aspect of the filter apparatus of the presentinvention, the first filter member is made of fiber, and mean fiberdiameter is from 0.2 to 3.0 μm and filled density is from 0.1 to 0.5g/cm³.

A filter apparatus in another broader aspect of the present inventioncomprises a container body having an opening at its one end, acylindrical member attached to the opening of the container body inliquid-tight manner, a first filter member placed in the cylindricalmember, through which plasma can move faster than corpuscles, and asecond filter member comprising the membrane for separating plasma orserum from blood according to the present invention, serially connectedwith the first filter member in subsequent stage in the cylindricalmember, and the first and the second filter members are disposed in afilter accommodation part, a blood accommodation part is formed inprecedent stage of the filter accommodation part, and a plasma or serumstorage part is formed on the downstream side of the filteraccommodation part.

In a still another specific aspect of the present invention, the filterapparatus further comprises a third filter member provided in precedentstage of the first filter member, made of fiber having a mean fiberdiameter of not less than 3.0 μm and a bulk density of not more than 0.3g/cm³.

In a further specific aspect of the filter apparatus of the presentinvention, the first filter member through which plasma can move fasterthan corpuscles has a property of adsorbing fibrinogen contained inblood, plasma or a fibrinogen solution.

In a further specific aspect of the filter apparatus of the presentinvention, an anticoagulant component is stored in at least a part-ofthe internal space of the filter apparatus.

In a further specific aspect of the filter apparatus of the presentinvention, an accelerator for accelerating coagulation of blood isstored in at least a part of the internal space.

In a further specific aspect of the filter apparatus of the presentinvention, an aqueous solution having an osmotic pressure of 200 to 300mOsm/kg is added to at least a part of the section from the bloodaccommodation part to the first and the second filter members.Preferably, the aqueous solution contains an internal standardsubstance.

In a further aspect of the filter apparatus of the present invention, avolume ratio of the blood accommodation part, filter accommodation partand plasma or serum storage part is in the range of 0.5-2:1:1-10.

In a further specific aspect of a blood testing container including thefilter apparatus according to the present invention, a strip ofimmunochromatographical diagnostic agent to be added to the separatedplasma or serum is stored in the blood testing container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section view showing one structural example ofa filter apparatus of the present invention;

FIG. 2 is a longitudinal section view showing another structural exampleof a filter apparatus of the present invention;

FIG. 3 is a longitudinal section view showing still another structuralexample of a filter apparatus of the present invention;

FIG. 4 is a schematic front section view of a filter apparatus in whicha blood separation filter according to another embodiment of the presentinvention is accommodated;

FIG. 5 is a schematic front section view for explaining the process ofseparating plasma or serum in the filter apparatus shown in FIG. 4;

FIG. 6 is a schematic front section view showing a filter apparatusaccording to still another embodiment of the present invention;

FIG. 7 is a schematic front section view of a blood testing system usinga filter apparatus according to a further embodiment of the presentinvention;

FIG. 8 is a schematic front section view for explaining a plasmaseparating method using the blood testing system shown in FIG. 7;

FIG. 9 is a schematic front section view of a blood testing containeraccording to the present invention;

FIG. 10 is a longitudinal section view showing a blood testing containeraccording to other embodiment of the present invention,; and

FIG. 11 is a longitudinal section view showing a blood testing containeraccording to a further embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be now described in more detail.

The plasma or serum separating membrane according to the presentinvention has a porosity of not more than 30%, preferably not more than25%. If the porosity is more than 30%, the load applied on erythrocytesbecomes large, and hemolysis is more likely to occur.

The plasma or serum separating membrane used in the present invention isfeatured by having a plurality of through holes penetrating from oneside to the other side of the membrane. Although the planar shape ofopening and the transverse section shape of the through holes are notparticularly limited, shapes having acute angels are unfavorable.Therefore, preferably, the planer shape of opening and the transversesection shape of the through holes are curved shapes such as circle orellipse.

Also the longitudinal section shape along the extending direction of thethrough holes is not particularly limited, and inside wall may be linearor curve in the longitudinal section. Furthermore, the direction inwhich the through holes extend may be orthogonal to the surface of themembrane or may be inclined from the orthogonal direction. The throughholes may have a longitudinal section of cut truncated cone.

As a method for forming the aforementioned through holes, irradiationwith energy beams such as ion beam irradiation or chemical treatmentssuch as alkaline erosion following the membrane formation can beexemplified without limited thereto. In other words, in the plasma orserum separating membrane according to the present invention, throughholes that penetrate from one side to the other side are formed byappropriate means as described above after formation of the membrane.

The through holes preferably have diameters in the range of 0.05 to 2.0μm. If the diameter is less than 0.05 μm, proteins, lipids and the likein the blood are likely to clog, while if the diameter is more than 2.0μm, erythrocytes can pass through the membrane due to theirdeformability. More preferably, the diameter is in the range of 0.1 to1.5 μm.

Preferably, in the above plasma or serum separating membrane, meansurface roughness of the membrane is not more than 100 nm. If the meansurface roughness exceeds 100 nm, the load applied on erythrocytesbecomes large, and hemolysis is more likely to occur.

The aforementioned plasma or serum separating membrane may be made ofmaterials including, but not limited to synthetic polymers or naturallypolymers. Examples of such materials include cellulose mixed esters,polyvinylidene difluoride, polytetrafluoroethylene, polycarbonate,polypropylene, polyester, nylon, glass and alumina.

The blood to be subjected to the separating operation in the presentinvention may be whole blood or a diluted blood sample. The blood is notlimited to human blood but may be animal blood. Also the blood may befresh blood or bloods added with anticoagulants such as heparin,ethylenediamine tetraacetate or citric acid.

In separation of plasma or serum from corpuscles in blood using theaforementioned plasma or serum separating membrane, the blood issupplied to one side of the membrane and the separation is accomplishedby filtration. The direction of blood flow and the direction offiltration in this filtration can be arbitrarily selected. In the caseof separating plasma or serum from corpuscles in whole blood, it ispreferred that the direction of blood flow and the direction offiltration differ from each other, and it is more preferred that thesedirections are orthogonal to each other. By employing differentdirections, it is possible to improve the separation efficiency.

In the case where the direction of blood flow and the direction offiltration are identical, clogging sometimes occurs in through holes.However, in the case of separating corpuscles in diluted blood, sinceclogging is not likely to occur, reliable separation is ensured withoutcausing any clogging even when the direction of blood flow and thedirection of filtration are selected to be identical. That is, theplasma or serum separating membrane according to the present inventionalso serves as a corpuscle blocking membrane.

In the above separating operation, filtration ends upon clogging byerythrocytes. In this case, hemolysis is liable to occur if an excesspressure is applied. In a separating membrane having conventional pores,hemolysis will occur upon application of only a small pressure; whereasin the case of using the plasma or serum separating membrane accordingto the present invention, hemolysis is unlikely to occur even when alarger pressure is applied. That is, hemolysis is unlikely to occur evenwhen a pressure of 60 kPa or less is applied for filtration. This isattributable to the fact that damages on erythrocytes are reducedbecause the shape of the plasma or serum separating membrane is athrough hole, and preferably the porosity is not more than 30% and thesurface of membrane is smooth.

If a pressure larger than 60 kPa is applied, erythrocytes may begradually broken. Therefore, the pressure to be applied is preferablynot more than 60 kPa. The plasma or serum thus obtained can be used toobtain accurate test values.

In a filter apparatus according to the present invention, a first filtermember through which plasma can move faster than corpuscles is seriallyconnected to the above plasma or serum separating membrane so that thefirst filter member is located at a precedent stage of the membrane.When uncoagulated blood is supplied, the blood first passes through thefirst filter member. At this time, plasma rapidly moves toward theplasma or serum separating membrane, and passes through the plasma orserum separating membrane according to the present invention. In thismanner, it is possible to efficiently separate plasma from corpuscles.In this filter apparatus, the filtration ends when erythrocytes clog thethrough holes of the plasma or serum separating membrane afterfiltration of plasma.

As to the first filter member through which plasma can move faster thancorpuscles, for example, synthetic polymers having fine fiber diameter,fibers made of glass or porous polymers can be used without beingparticularly limited thereto. When the first filter member is made of amaterial that adsorbs components to be measured in the blood, thematerial is preferably subjected to surface treatment. As an agent forsurface treatment, polyether-based or silicone-based lubricants,hydrophilic polymers such as polyvinylalcohol and polyvinylpyrrolidoneor natural hydrophilic polymers, or polymeric surfactants can be usedwithout being particularly limited thereto.

In the case where the first filter member is made of a synthetic polymeror fiber made of glass, the mean fiber diameter is preferably in therange of 0.2 to 3.0 μm. If the mean fiber diameter is less than 0.2 μm,hemolysis is more likely to occur. On the other hand, if the mean fiberdiameter is more than 3.0 μm, the fiber should be packed at high densityso as to separate plasma or serum from corpuscles. As a result, theamount of filter member increases as does cost. More preferably, thefiber diameter is in the range of 0.5 to 2.5 μm.

The first filter member may consist of two or more stages insofar as thefiber diameter of 0.2 to 3.0 μm and the packing density of 0.1 to 0.5g/cm are satisfied. In such a case, it is preferred that the packingdensity of downstream stage is higher than that of the upstream stage orthe packing density of the downstream stage is higher than that of theupstream stage. As a result, it is possible to further increase theseparation efficiency of plasma or serum.

In the present invention, preferably, the aforementioned first filtermember through which plasma can move faster than corpuscles has afibrinogen adsorbing ability. The fibrinogen adsorbing filter can bemade of, but not particularly limited to, the materials as follows.Polyester-based resins such as polyethyleneterephthalate andpolybutyleneterephthalate; nylon resins; polyurethane resins;polystyrene-based resins; resins composed of homopolymers or copolymersof poly(methacrylic acid) ester such as poly(methyl methacrylate); andresins composed of copolymers of polyethylene and vinyl acetate ormethacrylic acid ester. These resins may be used in combination ofplural kinds. Among others, polyester-based resins are desirably usedbecause they are superior in fibrinogen adsorbing ability and balance ofinfluence on test value.

Since a specimen obtained after removing fibrinogen by adsorption can behandled in the same manner as for serum, versatility for a variety ofclinical test is improved. Additionally, since such a specimen will notcoagulate even if it is left for a certain time, it can be applied to anautomated analyzer without anxiety. For example, the filter apparatus ofthe present invention may be configured in a blood collection tube, andin such a case, the blood having been collected is directly separated bydepressurizing the internal space of the blood collection tube to obtainplasma or serum required for measurement.

In one specific aspect of a filter apparatus according to the presentinvention, the filter apparatus comprises a container body having anopening at its one end, a cylindrical member attached to the opening ofthe container body in liquid-tight manner, and in the cylindrical membera first filter member, through which plasma can move faster thancorpuscles, and a second filter member comprising the aforementionedmembrane for separating plasma or serum from blood, serially connectedwith the first filter member in subsequent stage in the cylindricalmember are disposed. One example of such a filter apparatus is shown inFIGS. 1 to 3.

A filter apparatus 1 shown in FIG. 1 has a container body 2 having anopening 2 a at its upper end, and a cylindrical member 3 hermeticallyinserted into the opening 2 a of the container body 2. The containerbody can be implemented by a blood collection tube, a test tube and thelike. And as a material forming the container body 2, synthetic resins,glass and the like can be appropriately used. The cylindrical member 3can also be formed of appropriate materials such as synthetic resins andplastics. On the outer periphery of a lower end of the cylindricalmember 3 is formed a male screw, while on the inner periphery near theopening of the container body 2 is formed a female screw. Thecylindrical member 3 is pushed and fixed into the container body 2 bymeans of these male and female screws. By designing the screwing partbetween the male screw and the female screw to be hermetically sealed,the outer periphery of the cylindrical member 3 is hermetically fixed tothe inner periphery of the container body 2.

In the cylindrical member 3, a filter member 4 is accommodated in anupper part, and a plasma or serum separating membrane 5 is disposedunder the filter member 4, namely disposed subsequent and serially tothe filter member 4. The outer peripheral edge of the plasma or serumseparating membrane 5 is in close contact with the inner peripheral edgeof the cylindrical member 3. Above the A filter member 4, a plug member6 is attached to the opening of the upper end of the cylindrical member3. This provides hermetical sealing of the opening of the upper end ofthe cylindrical member 3.

By depressurizing the internal space of the container body 2, the bloodcollected in the cylindrical member 3 is filtered, and thereby plasma orserum can be separated from corpuscles in accordance with the presentinvention.

In a filter apparatus 7 illustrated in FIG. 2, a cylindrical member 9 ishermetically fixed to the container body 2 by means of a ring-shapedsealing member 8 having rubber elasticity. In the cylindrical member 9,a smaller diameter portion 9 b is connected via a step 9 a at a lowerposition than the part where the filter member 4 and the plasma or serumseparating membrane 5 are inserted. The step 9 a is opposite to theupper end 2 b of the container body 2, and the ring-shaped sealingmember 8 implemented by an O-ring, for example is disposed between thestep 9 a and the upper end 2 b. The diameter of the smaller diameterportion 9 b of the cylindrical member 9 is dimensioned to be pressedinto the opening 2 a of the container body 2. Therefore, it is possibleto hermetically fix the outer periphery of the cylindrical member 9against the inner periphery of the container body 2 by pressing thecylindrical member 9 into the container body 2 and compressing thering-shaped sealing member 8 between the step 9 a and the upper end 2 bof the container body 2. In a larger diameter portion 9 c having alarger diameter than the smaller diameter portion 9 b of the cylindricalmember 9, the filter member 4 and the plasma or serum separatingmembrane 5 are disposed. The upper end of the cylindrical member 9 isclosely plugged with the plug member 6.

In a filter apparatus 10 illustrated in FIG. 3, the cylindrical member 3is inserted into the container body 2 and hermetically fixed to thecontainer body 2 by a plug member 11. Concretely, the plug member 11 hasa gripping portion 11 a and an intermediate portion 11 b having asmaller diameter than the gripping portion 11 a, and a reduced diameterportion 11 c having a diameter which is smaller than that of theintermediate portion 11 b. The plug member 11 is made of a materialhaving rubber elasticity such as synthetic rubber or natural rubber. Thediameter of the reduced diameter portion 11 c has such a diameter thatcan be pressed into the opening of the upper end of the cylindricalmember 3. The intermediate portion 11 b has a such a diameter that canbe pressed into the container body 2. The gripping portion 11 a isdimensioned to have a larger diameter than the outside diameter of thecontainer body 2.

Consequently, as shown in FIG. 3, by pressing the reducedsmaller-diameter portion 11 c into the cylindrical member 3, andpressing the intermediate portion 11 b into the container body 2 via theopening 3 a of the container body 2, the cylindrical member 3 is fixedlydisposed in the container body 2.

As is apparent from the filter apparatuses 1, 7 and 10 illustrated inFIGS. 1 to 3, a filter apparatus according to the present invention canbe structured in various fashions. It is to be noted that the shapes ofthe container body, cylindrical member and the like are not limited tothose shown in the drawings.

In a filter apparatus according to the present invention, preferably,the aforementioned first filter member through which plasma or serum canmove faster than corpuscles and a second filter member formed of aplasma or serum separating membrane are serially connected, and onupstream side of the first filter member is provided a third filtermember having mean fiber diameter of not less than 3.0 μm and bulkdensity of not more than 0.3 g/cm^(3.)

The this filter is not particularly limited insofar as it has mean fiberdiameter of not less than 3.0 μm and bulk density of not more than 0.3g/cm³. It is requested that the mean fiber diameter is not less than 3.0μm and the bulk density is not more than 0.3 g/cm³, however, the meanfiber diameter is desirably not more than 20 μm. If the mean fiberdiameter is more than 20 μm, a trace of fibrin and the like thatprecipitates in the blood can no longer be captured. If the mean fiberdiameter is less than 3.0 μm, hemolysis becomes more likely to occur. Ifthe bulk density is more than 0.3 g/cm³, clogging is more likely tooccur.

In the case where the aforementioned first to third filter members areprovided, the first filter member and the second filter member areserially connected so that the second filter member is on the downstreamside, and the third filter member is disposed on the upstream side ofthe first filter member.

Therefore, in separating plasma or serum from corpuscles in blood, bloodis supplied on the third filter member. The blood supplied on the thirdfilter member passes through the third filter member and the firstfilter member sequentially. In this case, even when thick blood or bloodfrom which fibrin is easy to precipitate is supplied, fibrin and so onare captured by the third filter member to reduce the occurrence ofclogging in the first filter member. Therefore, in the first filtermember, erythrocytes are not likely to receive excess pressure, so thatoccurrence of hemolysis can be reduced. In the first filter member,plasma or serum moves faster than corpuscles. Accordingly, plasma orserum passes through the second filter member and separated from theblood. The corpuscles having passed through the first filter member arecaptured by the second filter member and will not leak downstream thesecond filter member.

As described above, in the structure that the first and the secondfilter members are serially connected, since the third filter member isdisposed on the upstream side of the first filter member, it is possibleto securely separate plasma or serum from blood while suppressingbreakage of erythrocytes in the blood separating filter according to thepresent invention.

The filter apparatus according to the present invention is featured byaccommodating the aforementioned blood separating filter of the presentinvention. Concrete structure for accommodating the blood separatingfilter is not particularly limited.

FIG. 4 is a schematic front section view of a filter apparatus accordingto another embodiment of the present invention. A filter apparatus 21 isformed by using a syringe 22 for injection. In the syringe 22, a firstfilter member 23 and a second filter member 24 are disposed so that thesecond filter member 24 is on the downstream side. On the first filtermember 23 is disposed a third filter member 25.

As illustrated in FIG. 5, in use of the filter apparatus 21, blood issupplied from above the syringe 22, and a piston 26 of the syringe ispushed in. This applies pressure on the blood and separated plasma orserum can be collected on the side of a tip end 22 a of the syringe.

Alternative to the procedure of using the piston 26, plasma or serum canbe separated by suctioning from the side of the tip end 22 a of thesyringe 22. For example, by attaching an injection needle to the tip endof the syringe 22 and piercing a plug member of a vacuum bloodcollection tube (not shown) with the injection needle, plasma or serumcan be suctioned from the side of the tip end of the syringe andcollected in the vacuum blood collection tube.

FIG. 6 is a front section view of a filter apparatus in still anotherembodiment of the present invention. A filter apparatus 31 has acartridge made up of a case 32 and a case 33. The cases 32 and 33 aredetachably fastened by screwing or the like in a liquid-tight manner. Inthe filter apparatus 31, the first filter member 23, the second filtermember 24 and the third filter member 25 are disposed in a similarmanner as in the embodiment illustrated in FIG. 4. The filter apparatus31 has an inlet port 32 a through which blood is supplied and an outletport 33 a through which separated plasma or serum is discharged.

In use of this filter apparatus, the inlet port 32 a is connected with asyringe and the blood collected by the syringe is pushed by a piston,whereby plasma or serum is separated from the blood by means of thefirst to the third filter members 23 to 25 and collected via the outletport 33 a. Also in the filter apparatus 31, plasma or serum may beseparated by suctioning from the side of the outlet port 33 a.

The cases 32, 33 constituting the aforementioned filter apparatus 31 maybe realized by a commercially available filter cartridge.

In the first and the second embodiments, the first and the second filtermembers are serially connected in such a manner that the first and thesecond filter members directly contact with each other. However, thefirst filter member and the second filter member are not necessarilyconnected directly insofar as they are connected serially from upstreamside to the downstream side. FIG. 7 is a schematic front section view ofa blood testing system equipped with a filter apparatus of otherembodiment of the present invention in which the first and the secondfilter members are disposed at a distance.

In a blood testing system 41, a filter apparatus 44 is made up of asyringe 42 and a filter holder 43. In the syringe 42, the first filtermember 23 and the third filter member 25 are accommodated so that thethird filter member 25 is on the upstream side. To a tip end 42 a of thesyringe 42, an inlet port 43 a of the filter holder 43 is connected in aliquid-tight manner. In the filter holder 43, the second filter member24 is provided. Corpuscles in the blood having moved into the filterholder 43 are captured by the second filter member 24. Consequently,separated plasma or serum is collected via an outlet port 43 b of thefilter holder 43.

In the blood testing system 41, an injection needle 45 is attached tothe outlet port 43 b of the filter holder 43. And the needle end of theinjection needle 45 pierces a plug member 47 attached to a plasma orserum storage container 46. The plug member 47 is made of an elasticmaterial and attached so as to hermetically seal the upper end openingof the storage container 46.

On the other hand, fitted into the plug member 47 is a flow channel 49connected to a constant pressure suction pump 48. As shown in FIG. 8, bydriving the constant pressure suction pump 48 after blood A is suppliedinto the syringe 42, the internal space of the storage container 46 isdepressurized to cause suctioning of the blood. The suctioned bloodsequentially passes through the third filter member 25, the firstfiltering member 23 and the second filter member 24, and separatedplasma or serum is finally collected into the storage container 45.

Accordingly, by removing the injection needle 45 and the flow channel 49from the storage container 46, it is possible to obtain separated plasmaor serum within the storage container 46.

FIG. 9 is a schematic front section view of one embodiment of a bloodtesting container according to the present invention. A blood testingcontainer 51 has an outer tube 52 and a cylindrical member 53 insertedinto the outer tube 52. The outer tube 52 is formed of a cylindricalcontainer having a bottom and an opening 52 a at its upper end. Thecylindrical member 53 has a cylindrical shape and has an opening 53 a atits upper end. At a lower end of the cylindrical member 53 is provided adownward projection 53 b which detachably fixed to the cylindricalmember 53. In the cylindrical member 53, the third filter member 25, thefirst filter member 23 and the second filter member 24 constituting theblood separating filter of the present invention are sequentiallydisposed from top down. In this manner, the blood separating filterconfigured according to the present invention is accommodated in thecylindrical member 53. Additionally, below the second filter member 24is formed a plasma or serum retaining part 53 c for retaining filtratedplasma or serum. The internal space of the blood testing container 51 isdepressurized, and the openings 52 a and 53 a of the outer tuber 52 andthe cylindrical member 53 are hermetically sealed by a plug member 54.

Therefore, in the blood testing container 51, blood is introduced into ablood accommodation part 56 extending above the blood separating filterby piercing the plug member 54 with a vacuum blood collection needle orthe like. Then by inserting a blood collection needle into the plugmember 54 or by forming a through hole penetrating the plug member 54after removing the vacuum blood collection needle to allow communicationbetween the internal space of the cylindrical member 53 and theatmosphere, filtration of the collected blood through the bloodseparating filter proceeds. Then plasma or serum obtained by filtrationflows down to a plasma or serum storage part 57 provided below via theplasma or serum retaining part 53 c.

The blood testing container according to the present invention is notlimited to the structure shown in FIG. 9 as to its concrete structureinsofar as the aforementioned blood separating filter is provided. Avariety of other structures can be adopted. For example, the first tothe third filter members 23 to 25 may be disposed in the storagecontainer in which separated plasma or serum is stored, or the containeraccommodating the first to the third filter members may be inserted intoa container storing separated plasma or serum to form adouble-structured blood testing container.

FIG. 10 is a longitudinal section view of a blood testing containeraccording to one embodiment of the present invention. A blood testingcontainer 61 is configured by using a blood collection container havinga container body 62 and a cylindrical member 63. The container body 62is formed of a tubular container having a bottom and an opening 62 a atits upper end.

In the vicinity of the opening 62 a at the upper end of the containerbody 62 is provided a female screw 62 b on the inner periphery.

The cylindrical member 63 is hermetically fixed to the container body 62by being screwed into the opening 62 a of the container body 62. Forachieving this fixation, a male screw 63 which meshes with the femalescrew 62 b is formed on the outer periphery in the lower part of thecylindrical member 63.

The cylindrical member 63 has an opening 63 b at its upper end. Belowthe cylindrical member 63 is formed a plasma or serum dropping part 63 cso as to project downward. The plasma or serum dropping part 63 c isbent so that its tip end is directed to the inner wall of the containerbody 62. The tip end of the plasma or serum dropping part 63 c islocated near a specimen supplying part 64 a of a blood testing agentstrip 64 placed inside the container body 62.

The container body 62 and the cylindrical member 63 can be made ofsynthetic resins, glass and the like without being particularly limitedthereto. However, in order to facilitate that the test result is checkedby eyes from outside, preferably, at least the container body 62 is madeof a transparent material, and in order to check the blood separationprocess by eyes, preferably, the cylindrical member 63 is also formed ofa transparent material.

For hermetically sealing the opening 63 b of the cylindrical member 63,a plug member 65 is attached to the opening 63 b.

The plug member 65 is formed of an elastic material such as rubber orelastomer. As the elastic material, any elastic material can be usedinsofar as it hermetically seals the opening 63 b and keeps the reducedpressure in the blood collection container formed of the container body62 and the cylindrical member 63.

In the cylindrical member 63, a filter apparatus 66 is disposed. Thefilter apparatus 66 has such a structure that the aforementioned firstfilter member 23 and the second filter member 24 are serially connected.

In the present embodiment, a blood collection container is made up ofthe above container body 62 and the cylindrical member 63. The internalspace of the blood collection container is depressurized. The degree ofdepressurization is such that the plug member 65 is pierced with avacuum blood collection needle and the blood is collected by thepressure difference between inside and outside. Concretely, the degreeof depressurization is about 1 to 90 kPa.

In the present embodiment, the blood collection container made up of thecontainer body 62 and the cylindrical member 63 has a first internalspace A and a second internal space B in the container. Specifically, afilter 66 consisting of the first filter member 23 and the second filtermember 24 is disposed at the boundary between the first internal space Aand the second internal space B. In the second space B, a blood testingagent strip 64 is disposed. In the present invention, the blood testingagent strip 64 is disposed so that it extends in the vertical directionand a specimen supplying part 64 a is on the side of its upper end inthe container body 62.

As the aforementioned blood testing agent strip 64, blood testing agentstrips used in detection of components in plasma or serum or substancescontained in plasma or serum can be appropriately used.

In the present embodiment, a strip of immunochromatographical diagnosticagent is used as the above blood testing agent strip. Therefore, aspecific component in plasma or serum can be detected using the bloodtesting agent strip 64 by immunochromatography.

In the present embodiment, the blood testing agent strip 64 is used,however, a blood testing agent of other embodiment may be disposed inthe second space B in place of the blood testing agent strip 64.

Next, a blood testing method using the blood testing container 61according to the present embodiment will be explained.

In conducting a blood test, the plug member 65 is pierced with a vacuumblood collection needle. At this time, since the internal space of theblood testing container 61 is depressurized, blood passes the vacuumblood collection needle and introduced to the first space A of the bloodtesting container 61. After blood is collected, the blood is supplied tothe first filter member 23 where plasma or serum moves faster thancorpuscles, and the plasma or serum is quickly introduced to the secondfilter member 24. In the second filter member 24, plasma or serum passesthrough the aforementioned through holes, and is supplied to thespecimen supplying part 64 a of the blood testing agent strip 64 via theplasma or serum dropping part 63 c. This filtration of blood rapidlyproceeds by the pressure difference between the first internal space Aand the second internal space B.

In other words, after collecting blood by means of the vacuum bloodcollection needle, the plug member is pierced with a blood collectionneedle or the like to allow communication between the external and theinternal space A. This reduces the degree of depressurization togenerate a pressure difference between the first internal space A andthe second internal space B. Owing to this pressure difference, namelythe residual pressure in the second internal space, the filtrationproceeds quickly. Then, as the through holes of the second filter member24 are clogged with erythrocytes, the filtration ends.

As described above, in the blood testing method of the presentembodiment, after collecting blood into the internal space A of theblood testing container 61 with the use of a vacuum blood collectionneedle or the like, plasma or serum is quickly filtered from the bloodwithout requiring cumbersome operation such as centrifugal separation,and the plasma or serum is supplied to the blood testing agent strip 64placed in the second internal space B. Accordingly, the process fromblood collection to the end of the blood test can be carried outautomatically and safely without leading possibility of infection.

FIG. 11 is a longitudinal section view of a blood testing containeraccording to still another embodiment of the present invention. In theblood testing container 61 illustrated in FIG. 10, the cylindricalmember 63 is connected on an upper part of the container body 62,however, in a blood testing container 80 of the present embodiment, acylindrical member 83 is inserted into a container body 82. A plugmember 81 that closes an opening of the cylindrical member 83 closes notonly an opening 83 b of the cylindrical member 83 but also an opening 82a of the container body 82.

The plug member 81 is configured to have a gripping portion 81 a, alarger-diameter portion 81 b projecting downward the gripping portion 81a and having a smaller diameter than the gripping portion 81 a, and asmaller-diameter portion 81 c projecting downward from the bottomsurface of the larger-diameter portion 81 b and having a smallerdiameter than larger-diameter portion 81 b. The larger-diameter portion81 b is inserted into the opening 82 a and the smaller-diameter portion81 c is pressed into the opening 83 b of the cylindrical member 83. Inthis way, the blood collection container made up of the container body82 and the 83 is hermetically sealed in such a manner that a certaindegree of depressurization is kept in the blood collection container.

Other configuration is as same as that of the blood testing container 61of the embodiment illustrated in FIG. 10, and hence detailed explanationabout each part identical to that shown in FIG. 10 will be omitted bydesignating the part by the same reference numeral.

Also in the second blood testing container 80, since the internal spaceis depressurized in advance, after piercing the plug body with a vacuumblood collection needle and collecting blood as is the case of the bloodtesting container 61, filtration of the blood automatically proceedsupon piercing of the plug member with a conducting jig, and plasma orserum serving as a specimen is supplied the blood testing agent strip64. Accordingly, it is possible to safely complete the operation fromthe collection of blood to the blood test as is the case of the bloodtesting container 61 without requiring a centrifuge separator or acentrifuge operation.

As described above, the blood testing container according to the presentinvention can be embodied in various forms. When the blood testcontainer includes a blood accommodation part having an opening for theblood test container and accommodating collected blood, a filteraccommodation part accommodating the aforementioned first and secondfilter members or the first to third filter members, and a plasma orserum storage part located subsequent to the filter accommodation partand storing plasma or serum, a volume ratio of the blood accommodationpart, filter accommodation part and plasma or serum storage part ispreferably in the range of 0.5-2:1:1-10. The reason of this is asfollows: if the proportion of the blood accommodation part is less than0.5, the amount of blood is insufficient relative to the filter amount,so that no or only a small amount of specimen is obtained afterseparation. On the other hand, if the volume of the blood accommodationpart is more than 2.0 in the above ratio, blood exceeding the bloodseparation capability of the filter is supplied, so that the burden on asubject may increase.

In the blood testing container according to the present invention, asdescribed above, it is possible to separate blood by using pressuredifference. In this case, blood is driven by pressure difference betweenthe blood accommodation part and the plasma or serum storage part, toflow into the filter for achieving separation. As the separation ofblood proceeds, the internal pressure of the plasma or serum storagepart increases, and hence driving force of filtration decreases. Theaforementioned pressure difference depends on the volume of the plasmaor serum storage part. If the volume of the plasma or serum storage partis less than 1 in the above ratio, the driving force is insufficient forblood separation, leading the problem that no or only a small amount ofspecimen is obtained after separation. To the contrary, if thevolumetric proportion of the plasma or serum storage part is more than10, the driving force is sufficient for blood separation, however, sucha configuration is not favorable because the size may increase more thannecessary, the cost may rise, and the amount of waste after uses mayincrease.

In the blood testing container according to the present invention, it ispreferred that an aqueous solution having an osmotic pressure of 200 to350 mOsm/kg is added at at least one point in the course from bloodaccommodation part where the collected blood is supplied to the filteraccommodation part. In this case, the collected blood is mingled withthe aqueous solution in the process before the end of the bloodseparation and hence concentration of corpuscles in the blood decreases.That is, the hematocrit value decreases. When the filter apparatus isused for separating blood, the smaller the hematocrit the higher theseparation efficiency, and the amount of specimen obtained afterseparation dramatically increases. However, in a clinical test, the testvalue does not always change in correspondence with the dilution ratewhen plasma or serum is diluted. Therefore, dilution should be conductedwith care.

In the present invention, designating the amount of collected blood as1, the amount of the above aqueous solution to be added is preferably inthe range of 0.2 to 5. If the proportion of the aqueous solution to beadded is less than 0.2, almost no increase in the amount of obtainedspecimen is expected, whereas if the proportion of the adding amount ofthe aqueous solution is larger than 5, the blood is diluted in excess sothat abnormality occurs in the clinical test value. More preferably, theadding amount of the above aqueous solution is in the range of 0.5 to 3,when the amount of collecting blood is designated as 1.

The aqueous solution to be added is preferably has an osmotic pressurewhich is equal to that of the blood so that corpuscles, in particular,erythrocytes will not break when the aqueous solution is mingled withthe blood. Therefore, the osmotic pressure of the above aqueous solutionis preferably in the range of 200 to 350 mOsm/kg. If it is less than 200mOsm/kg, erythrocytes can expand and collapse, while if it is more than350 mOsm/kg, contents of the erythrocytes may solve out to giveabnormality on the clinical test value. More preferably, the osmoticpressure of the above aqueous solution is in the range of 250 to 300mOsm/kg.

The solute in the above aqueous solution is not particularly limited,however, solutes whose aqueous solution is strongly acidic or alkalineor reactive with components of the blood are unfavorable. In order tostabilize pH, a combination of inorganic substances having buffer effectis preferably used. Examples of such a combination include, but notlimited to, citric acid and disodium hydrogenphosphate; imidazole andhydrochloric acid; trimethylpyridine and hydrochloric acid; triethanolamine and hydrochloric acid; tris(hydroxymethyl)aminomethane andhydrochloric acid; and the like. However, such a combination is notparticularly limited insofar as it has a buffer effect at pH of 6 to 8.Also salts such as sodium chloride that will not influence on pH can bepreferably used.

Also an internal standard substance may be added to the aqueous solutionso that the volume ratio of the collected blood and the aqueous solutionis clearer when they are mingled. Such an internal standard substance isalso useful for accurately calculating a dilution rate of a plasma orserum obtained through separation of blood. With the internal standardsubstance, a clinical test value can be calculated accurately. Theinternal standard substance is not particularly limited, however, itshould be a component that does not exist in blood, it should be watersoluble, it should have a certain characteristic such as ultravioletabsorption, infrared absorption, near-infrared absorption, fluorescentwavelength, and the concentration thereof in plasma or serum should bemeasurable by a common measurement method. Examples of such internalstandard substance include benzotriazole-based compounds, benzoicacid-based compounds such as methyl p-dimethylbenzoate and octylp-dimethylaminobenzoate, substances having ultraviolet visibleabsorption such as oxobenzene, benzoic acid and salicylic acid, andwater-soluble metal complexes such as [Co(H₂O)₆]²⁺, [Co(NH₃)₅]²⁺ and[Fe(η-C₅H₅)₂]. Also pigments such as indigo, eosin, β-carotene,malachite green, methyl blue and the like can be used. Examples of thefluorescent substances include erhythrosin, rhodamine sulphate,rhodamine B, pinacyanol. Not limited to the internal standard substancesrecited above, any substance can be used without causing problemsinsofar as it does not exist in a living body and will not becomplicated with the substance to be measured.

In the filter apparatus according to the present invention, preferablyan anticoagulant component is added to at least a part of the filterapparatus. In this case, the anticoagulant component is added so as toprevent blood from coagulating. The anticoagulant component is added tothe part where the filter member is accommodated, for example in thepart where the first and the second filter members or the first to thethird filter members of the aforementioned filter apparatus areaccommodated, or to the blood accommodation part which is on upstreamside of the part where the filter member is accommodated. In the casewhere an anticoagulant component is added to the blood accommodationpart, the anticoagulant component is added to a part that accommodatesblood to be tested in the filter apparatus or in a blood testingcontainer having the filter apparatus. Therefore, it is possible toprevent the blood to be tested from coagulating immediately. Even in thecase where the anticoagulant component is added to the filteraccommodation part connecting with the blood accommodation part,coagulation of blood can be effectively prevented in a similar way.Furthermore, when filtration by the filter member is immediatelyconducted, the anticoagulant components may be added at a later stagethan the filter accommodation part.

Any anticoagulant component can be used without being particularlylimited insofar as it has an ability to substantially suppresscoagulation of blood. Examples of such anticoagulant component includeheparin metal salts such as sodium heparin and lithium heparin. As ananticoagulant component having decalcium ability, sodium citrate,ethylene diamine tetraacetate, oxalate, sodium fluoride and the like canbe exemplified.

The adding amount of the anticoagulant component is preferably in therange of 0.5 to 50 units with respect to 1 mL of collected blood in thecase of a heparin metal salt, although the adding amount differsdepending on the kind of the anticoagulant component. In the case of thesodium citrate, ethylene diamine tetraacetate, oxalate, sodium fluorideand the like, the adding amount is preferably about 0.5 to 20 mg withrespect to 1 mL of collected blood.

The filter apparatus or blood testing container of the present inventionmay partly be added with a coagulation promoting agent that promotescoagulation of blood contrarily to the anticoagulant component. Byadding the coagulation promoting agent, it is possible to make bloodcoagulate and to collect serum as a sample. By adding the coagulationpromoting agent, fibrinogen that is not completely removed in theprocess of separating serum from blood in the filter apparatus isprevented from passing the filter and flowing down to the plasma orserum storage part. Therefore, serum from which fibrinogen has beenremoved can be obtained with reliability, and hence the problem that thespecimen coagulates later can be avoided.

As the coagulation promoting agent, adsorptive inorganic substances suchas silica, thrombin and snake venom, as well as thrombin-like enzymessuch as papain can be exemplified.

In the case of using a coagulation promoting agent of enzyme type suchas thrombin, the coagulation promoting agent is preferably added on thedownstream side of the filter. If the coagulation promoting agent isadded on the upstream side of the filter, coagulation of blood rapidlyproceeds and the filter is clogged with the coagulated blood. This maypossibly stop the separation of the blood. In contrast to this, when thecoagulation promoting agent is added in the vicinity of the downstreamside within the filter accommodation part, only the fibrinogen notremoved by the filter can be coagulated by the action of the coagulationpromoting agent, so that the fibrinogen can be removed securely withinthe filter member.

The present invention will be better understood from the followingexplanation of concrete examples of the present invention. It is to benoted that the present invention is not limited to the followingexamples.

EXAMPLE 1

A separation membrane made of polycarbonate having a thickness of 10 μm(manufactured by Millipore Corporation, product number: GTTP04700,separation membrane having a plurality of through holes with a circularcross section shape of 0.2 μm in pore size) was prepared. The separationmembrane was cut into a piece of 13 mm in diameter and the piece was setinto a commercially available filter cartridge (manufacture by MilliporeCorporation, trade name: Sphinex filter holder S×0130000).

EXAMPLE 2

An evaluation sample was prepared in the same manner as Example 1 exceptthat the diameter of the through holes was changed to 0.6 μm.

EXAMPLE 3

An evaluation sample was prepared in the same manner as Example 1 exceptthat the diameter of the through holes was changed to 2.0 μm.

EXAMPLE 4

In a 10 mL-syringe having an inner diameter of 14.5 mm (manufactured byJMS Corporation, made of polypropylene), a separation membrane made ofpolycarbonate having a number of through holes of 0.2 μm in diameter andused in Example 1 was set, and 1.0 g of polyester fiber having meanfiber diameter of 1.8 μm was charged on the separation membrane,followed by compression into a volume of 4.0 cm³, thereby forming afilter member. The syringe thus prepared was used as an evaluationsample.

EXAMPLE 5

An evaluation sample was obtained in the same manner as Example 4 exceptthat the diameter of the through holes was changed to 0.8 μm.

Comparative Example 1

A separation membrane made of polyvinylidene fluoride having a number ofcontinuous air holes of 0.22 μm in pore size (manufactured by MilliporeCorporation under the trade name of Durapore, 125 μm thick) was cut tohave a diameter of 13 mm, and placed into a filter cartridge in the samemanner as Example 1 to obtain an evaluation sample.

Comparative Example 2

An evaluation sample was obtained in the same manner as Comparativeexample 1 except that the pore size was changed to 0.65 μm.

Comparative Example 3

An evaluation sample was obtained in the same manner as Example 1 exceptthat the pore size was changed to 3.0 μm.

Comparative Example 4

In a 10 mL-syringe having an inner diameter of 14.5 mm (manufactured byJMS Corporation, made of polypropylene), a separation membrane havingcontinuous air holes of 0.22 μm in pore size and used in Comparativeexample 1 was set, and then a filter member was set on the separationmember by charging 1.0 g of polyester fiber having mean fiber diameterof 1.8 μm on the separation membrane and compressing into a volume of4.0 cm³, whereby an evaluation sample was obtained.

Comparative Example 5

An evaluation sample was obtained in the same manner as Example 4 exceptthat the separation membrane having through holes of 3.0 μm in pore sizeused in Comparative example 3 was used.

Test Example 1

Each evaluation sample of Examples 1 to 3 and Comparative example 1 to 3was used. Using 100 μL of a diluted blood having hematocrit of 10%,filtration was conducted by applying the pressures shown in Table 1below. The state of obtained plasma was compared with that of the plasmaobtained by centrifugal separation (10 min. at 3,000 rpm) of the abovediluted blood to determine whether or not hemolysis occurs.

Results are shown in Table 1 below. TABLE 1 Pore Filtration SeparationState Shape of Hole Size Pressure of Plasma Ex. 1 Through Hole 0.2 μm 60kPa Hemolysis Not Observed Ex. 2 Through Hole 0.6 μm 60 kPa HemolysisNot Observed Ex. 3 Through Hole 2.0 μm 20 kPa Hemolysis Not ObservedComp. Ex. 1 Continuous 0.22 μm  60 kPa Hemolysis Air Hole ObservedContinuous 0.22 μm  20 kPa Hemolysis Air Hole Observed Comp. Continuous0.65 μm  20 kPa Hemolysis Ex. 2 Air Hole Observed Comp. Through Hole 3.0μm 20 kPa Erythrocytes Ex. 3 Leaked Out

Test Example 2

Using the evaluation examples of Examples 4, 5 and Comparative examples4, 5, 4 mL of human blood having a hematocrit of 46.7% was supplied andfiltration was conducted by the pressures as shown in Table 2 below. Theplasma thus obtained was compared with the plasma obtained bycentrifugal separation (10 min. at 3,000 rpm) of the same blood, andpresence/absence of hemolysis was checked by eyes. Results are shown inTable 2 below. TABLE 2 Pore Filtration Separation State Shape of HoleSize Pressure of Plasma Ex. 4 Through Hole 0.2 μm 60 kPa Hemolysis NotObserved Ex. 5 Through Hole 0.8 μm 60 kPa Hemolysis Not Observed Comp.Ex. 4 Continuous 0.65 μm  20 kPa Hemolysis Air Hole Observed Comp. Ex. 5Through Hole 3.0 μm 20 kPa Erythrocytes Leaked Out

EXAMPLE 6

A corpuscles blocking membrane made of polycarbonate having throughholes of 0.2 μm in pore size and having a porosity of 14% was prepared.The corpuscles blocking membrane is available from Millipore Corporationunder the trade name of Isopore GTTP and has a thickness of 10 μm. Thecorpuscles blocking membrane was cut to have a diameter of 13 mm and setinto a commercially available filter holder (manufactured by MilliporeCorporation under the trade name of Sphinex filter holder, effectivefiltration area: about 0.7 cm²) to thereby obtain a sample forevaluation.

EXAMPLE 7

An evaluation sample was obtained in the same manner as Example 6 exceptthat the pore size and the porosity were changed to 0.8 μm and 15%,respectively. Isopore ATTP (trade name) manufactured by MilliporeCorporation was used as the corpuscles blocking membrane.

EXAMPLE 8

An evaluation sample was obtained in the same manner as Example 6 exceptthat the pore size and the porosity were changed to 1.2 μm and 23%,respectively. Isopore RTTP (trade name) manufactured by MilliporeCorporation was used as the corpuscles blocking membrane.

EXAMPLE 9

An evaluation sample was obtained in the same manner as Example 6 exceptthat the pore size and the porosity were changed to 2.0 μm and 8%,respectively. Isopore TTTP (trade name) manufactured by MilliporeCorporation was used as the corpuscles blocking membrane.

EXAMPLE 10

In a 10 mL-syringe having an inner diameter of 14.5 mm, a corpusclesblocking membrane having a pore size of 0.2 μm and porosity of 14% andused in Example 6, cut to have a diameter of 14.5 mm was set, and then afilter member was set by charging 1.0 g of polyester fiber having meanfiber diameter of 1.8 μm and compressing into a volume of 4.0 cm³,whereby an evaluation sample was obtained.

EXAMPLE 11

An evaluation sample was obtained in the same manner as Example 10except that the pore size and the porosity were changed to 0.8 μm and16%, respectively.

EXAMPLE 12

An evaluation sample was obtained in the same manner as Example 10except that the pore size and the porosity were changed to 2.0 μm and8%, respectively.

Comparative Example 6

An evaluation sample was obtained in the same manner as Example 6 exceptthat a 125 μm-thick polyvinylidene fluoride membrane having a pluralityof holes (manufactured by Millipore Corporation under the trade name ofDurapore GVWP, 0.22 μm pore size and 70% porosity) was used as thecorpuscles blocking membrane.

Comparative Example 7

An evaluation sample was obtained in the same manner as Example 6 exceptthat a 150 μm-thick cellulose-mixed ester film having a plurality ofholes (manufactured by Millipore Corporation under the trade name ofMF-Millipore DAWP, 0.65 μm pore size and 81% porosity) was used as thecorpuscles blocking membrane.

Comparative Example 8

An evaluation sample was obtained in the same manner as Comparativeexample 6 except that the pore size and the porosity were changed to 5.0μm and 70%, respectively.

Comparative Example 9

An evaluation sample was obtained in the same manner as Example 6 exceptthat the pore size and the porosity were changed to 3.0 μm and 14%,respectively.

Comparative Example 10

An evaluation sample was obtained in the same manner as Example 10except that a corpuscles blocking membrane made of polyvinylidenefluoride having a pore size of 0.22 μm, porosity of 70% and thickness of125 μm, namely, the corpuscles blocking membrane used in Comparativeexample 6 was used.

Comparative Example 11

An evaluation sample was obtained in the same manner as Example 10except that a corpuscles blocking membrane made of cellulose-mixed esterhaving a pore size of 0.65 μm, porosity of 81% and thickness of 150 μm,namely, the corpuscles blocking membrane used in Comparative example 7was used.

Comparative Example 12

An evaluation sample was obtained in the same manner as Example 10except that a 9 μm-thick polycarbonate film having a plurality of holes(manufactured by Millipore Corporation under the trade name of IsoporeTSTP, 3.0 μm pore size and 14% porosity) was used as a corpusclesblocking membrane.

Test Example 3

Blood obtained from a healthy individual was separated by centrifugationinto plasma and corpuscle components. Using the corpuscles blockingmembrane of Examples 6 to 9 and Comparative examples 6 to 8, 200 μL ofplasma component obtained by the centrifugal separation was applied andfiltered at pressures listed in Table 3 below. Before ending of thefiltration, another 200 μL of blood not subjected to centrifugalseparation was added and filtration was continued. After 10 minutes, thestate of plasma having been filtered was compared with that of thecentrifuged plasma to determine whether hemolysis occurred. The resultsare shown in Table 3. TABLE 3 Pore Filtration Separation State SizePorosity Pressure of Plasma Ex. 6 0.2 μm 14% 60 kPa Hemolysis NotObserved Ex. 7 0.8 μm 16% 60 kPa Hemolysis Not Observed Ex. 8 1.2 μm 23%60 kPa Hemolysis Not Observed Ex. 9 2.0 μm 8% 60 kPa Hemolysis SlightlyObserved 40 kPa Hemolysis Not Observed Comp. 0.22 μm  70% 20 kPaHemolysis Observed Ex. 6 Comp. 0.65 μm  81% 20 kPa Hemolysis ObservedEx. 7 Comp. 5.0 μm 70% 20 kPa Erythrocytes Leaked Out Ex. 8 Comp. 3.0 μm14% 20 kPa Erythrocytes Leaked Out Ex. 9

As is apparent from Table 3, in Examples 5 to 9, plasma in whichhemolysis did not occur could be obtained even when a pressure of 60 kPaor 40 kPa was applied, while in Compartive examples 6 to 8, hemolysis orleakage of erythrocytes was observed at a pressure of as low as 20 kPa.

Test Example 4

Using filter apparatus incorporating the corpuscles blocking membranesaccording to Examples 10 to 12 and Comparative examples 10 to 12, 4 mLof human blood having a hematocrit of 46.7% was filtrated at thepressures listed in Table 4 below. After leaving for 10 minutes, thestate of the obtained plasma was compared with that of the plasma havingsubjected to centrifugal separation (3,000 rpm×10 min.) to determinewhether hemolysis occurred. TABLE 4 Pore Filtration Separation StateSize Porosity Pressure of Plasma Ex. 10 0.2 μm 14% 60 kPa Hemolysis NotObserved Ex. 11 0.8 μm 16% 60 kPa Hemolysis Not Observed Ex. 12 2.0 μm8% 60 kPa Hemolysis Not Observed Comp. Ex. 10 0.22 μm  70% 20 kPaHemolysis Observed Comp. 0.65 μm  81% 20 kPa Hemolysis Observed Ex. 11Comp. 3.0 μm 14% 20 kPa Erythrocytes Leaked Ex. 12 Out

In Examples 10 to 12, hemolysis did not occur and filtrationautomatically stopped after plasma was filtrated. Contrarily, inComparative examples 10 to 12, hemolyzed plasma was gradually filtratedor erythrocytes were directly filtered.

Next, concrete examples will be explained.

EXAMPLE 13

The blood testing system 41 illustrated in FIG. 7 was constructed. Thesyringe 42 was charged with 1.0 g of polyethylene terephthalate fiberhaving mean fiber diameter of 1.8 μm for forming the first filtermember, and then with 0.22 g of fiber composed of polyethyleneterephthalate having mean fiber diameter of 3.5 μm and bulk density of0.1 g/cm³ for forming the third filter member. Then these fibermaterials were compressed so that the total volume was 4 cm³ to producethe first filter member 23 and the third filter member 25.

As the filter holder 43, Sphinex filter holder (trade name) manufacturedby Millipore Corporation was used, and as the second filter, a filterhaving pore size of 0.4 μm and porosity of 13% (manufactured byMillipore Corporation under the trade name of Isopore HTTP) was punchedout to a diameter of 13 mm and set. The above syringe 42 and the filterholder 43 were connected as shown in FIG. 7, thereby constructing afilter apparatus.

EXAMPLE 14

A filter apparatus was formed in the same manner as Example 13 exceptthat 0.02 g of fiber having mean fiber diameter of 6.0 μm and bulkdensity of 0.1 g/cm³ was used as a material forming the third filtermember.

EXAMPLE 15

A filter apparatus was formed in the same manner as Example 13 exceptthat 0.05 g of fiber having mean fiber diameter of 10.0 μm and bulkdensity of 0.1 g/cm³ was used as a material forming the third filtermember.

Comparative Example 13

A filter apparatus was formed in the same manner as Example 13 exceptthat the third filter member was not formed.

Test Example 5

Using each of the filter apparatuses according to Examples 13 to 15 andComparative example 13, the plasma or serum storage container 46 and thesuction pump 48 were connected to each other as shown in FIG. 7 and FIG.8, and 4 mL of blood having hematocrit of about 40% was added into thesyringe 42, after which suction filtration was conducted at a pressureof 50 kPa. The plasma thus obtained was compared with the plasmaobtained by subjecting the same blood to centrifugal separation, andpresence/absence of hemolysis was observed.

Test Example 6

Using each of the filter apparatuses according to Examples 13 to 15 andComparative example 13, blood having hematocrit of about 40% was fedinto a glass container and left for two minutes for promotingcoagulation, after which 4 mL of the blood whose coagulation waspromoted was added to each filter apparatus and suction filtration at apressure of 50 kPa was followed in the same manner as Example 5. Theplasma thus obtained was compared with the plasma obtained by subjectingthe same blood to centrifugal separation, and presence/absence ofhemolysis was observed.

The results are shown in Table 5 below.

Presence/absence of hemolysis was determined in the following manner.

No hemolysis: no difference was observed compared to plasma obtained bycentrifugal separation.

Slight hemolysis: plasma was slightly reddish compared to plasmaobtained by centrifugal separation.

Weak hemolysis: plasma was apparently reddish compared to plasmaobtained by centrifugal separation. TABLE 5 Result of Result of TestExample 5 Test Example 6 Ex. 13 No Hemolysis Slight Hemolysis Ex. 14 NoHemolysis No Hemolysis Ex. 15 No Hemolysis No Hemolysis Comp. Ex. 13 NoHemolysis Weak Hemolysis

In the following Examples 16 to 21 and Comparative examples 14 and 15,surface roughness of a plasma or serum separation membrane was measuredin the following manner.

More specifically, mean surface roughness Ra was measured as a shape offilter surface by AFM and DFM with the use of a scanning-type probemicroscope. Herein the mean surface roughness Ra is mean surfaceroughness Ra along central line based on the standard of JIS B0601,extended three-dimensionally so as to be applicable to the measurementsurface, and hence is a mean value of absolute values of deviation froma reference surface to a designated surface. The used apparatus wasSPI3800N and SPA400 manufactured by SII Corporation. Used probes are asfollows. TABLE 6 Deep Needle Length of Spring End Diameter MaterialCantilever Constant AFM 10 nm Silicon Nitride 100 μm 0.09 N/m DFM 10 nmSilicon 100 μm 20.0 N/m

The scanning frequency in the measurement was 1 Hz, and then number ofacquiring data X/Y was 256/256.

EXAMPLE 16

A filter made of polycarbonate having a pore size of 0.4 μm, porosity of18% and mean surface roughness of 58.62 nm was cut to have a diameter of13 mm, and set into a commercially available filter cartridge, to obtainan evaluation sample.

EXAMPLE 17

A filter made of polycarbonate having a pore size of 0.4 μm, porosity of15% and mean surface roughness of 24.63 nm was cut to have a diameter of13 mm, and set into a commercially available filter cartridge, to obtainan evaluation sample.

EXAMPLE 18

A filter made of polycarbonate having a pore size of 0.4 μm, porosity of15% and mean surface roughness of 27.53 nm was cut to have a diameter of13 mm, and set into a commercially available filter cartridge, to obtainan evaluation sample.

EXAMPLE 19

A commercially available 10 mL-plastic syringe was charged with 1.0 g ofpolyester fiber having fiber diameter of 1.8 μm with compression toachieve a volume of 4 mL, and the filter sample according to Example 16was set on the downstream side, to obtain an evaluation sample.

EXAMPLE 20

A commercially available 10 mL-plastic syringe was charged with 1.0 g ofpolyester fiber having fiber diameter of 1.8 μm with compression toachieve a volume of 4 mL, and the filter sample according to Example 17was set on the downstream side, to obtain an evaluation sample.

EXAMPLE 21

A commercially available 10 mL-plastic syringe was charged with 1.0 g ofpolyester fiber having fiber diameter of 1.8 μm with compression toachieve a volume of 4 mL, and the filter sample according to Example 18was set on the downstream side, to obtain an evaluation sample.

Comparative Example 14

A filter made of polyvinylidene difluoride having a pore size of 0.45μm, porosity of 70% and mean surface roughness of 147.70 nm was cut tohave a diameter of 13 mm, and set into a commercially available filtercartridge, to obtain an evaluation sample.

Comparative Example 15

A commercially available 10 mL-plastic syringe was charged with 1.0 g ofpolyester fiber having fiber diameter of 1.8 μm with compression toachieve a volume of 4 mL, and the filter sample according to Comparativeexample 14 was set on the downstream side, to obtain an evaluationsample.

Test Example 7

Using each of the separation membranes according to Examples 16 to 18and Comparative example 14, 500 μL of blood having hematocrit of 10% wasdeveloped on each of the separation membranes, after which filtrationwas conducted at respective pressures shown in Tables 7 and 8 below. Theplasma thus obtained was compared with the plasma obtained by subjectingthe same blood to centrifugal separation, and checked for hemolysis.TABLE 7 Mean Surface Pore Filtration Separation Roughness Size PressureState of Plasma Ex. 16 58.62 nm 0.4 μm 60 kPa No Hemolysis Ex. 17 24.63nm 0.4 μm 60 kPa No Hemolysis Ex. 18 27.53 nm 0.4 μm 60 kPa No HemolysisComp. Ex. 14 147.70 nm  0.45 μm  60 kPa Hemolysis

Test Example 8

Using each of the separation filters according to Examples 19 to 21 andComparative example 15, 4 mL of blood collected from a healthy volunteerwas developed on each of the separation filters, after which filtrationwas conducted at respective pressures shown in Table 8. The plasma thusobtained was compared with the plasma obtained by subjecting the sameblood to centrifugal separation, and checked for hemolysis. TABLE 8 MeanSeparation Amount Remaining Surface Pore Filtration State of ofFibrinogen Roughness Size Pressure Blood Specimen Amount* Ex. 19 58.62nm 0.4 μm 60 kPa No 0.52 mL Quantification Hemolysis Limit or Less Ex.20 24.63 nm 0.4 μm 60 kPa No 0.53 mL Quantification Hemolysis Limit orLess Ex. 21 27.53 nm 0.4 μm 60 kPa No 0.52 mL Quantification HemolysisLimit or Less Comp. 147.70 nm  0.45 μm  60 kPa Hemolysis 0.52 mLQuantification Ex. 15 Limit or Less*Quantification Limit of Fibrinogen: 10 mg/dL

EXAMPLE 22

To a commercially available 10 mL-plastic syringe, the filter sample ofExample 16 was set. Glass fiber having fiber diameter of 1.0 μm andporosity of 90.5%, and then 1.0 g of polyester fiber having fiberdiameter of 1.8 μm were placed on the upstream side of the filter samplewhile compressed to a volume of 4 mL, to thereby obtain an evaluationsample.

EXAMPLE 23

To a commercially available 10 mL-plastic syringe, the filter sample ofExample 16 was set. Glass fiber having fiber diameter of 0.6 μm andporosity of 90.4%, and then 1.0 g of polyester fiber having fiberdiameter of 1.8 μm were placed on the upstream side of the filter samplewhile compressed to a volume of 4 mL, to thereby obtain an evaluationsample.

EXAMPLE 24

To a commercially available 10 mL-plastic syringe, the filter sample ofExample 16 was set. 0.2 g of fiber having fiber diameter of 1.8 μm wascompressed into a volume of 0.4 mL, and then 1.0 g of polyester fiberhaving fiber diameter of 1.8 μm were placed on the upstream side of thefilter sample while compressed to a volume of 4 mL, to thereby obtain anevaluation sample. TABLE 9 Separation Amount Remaining Mean Surface PoreFiltration State of of Fibrinogen Roughness Size Pressure Blood SpecimenAmount* Ex. 22 58.62 nm 0.4 μm 60 kPa No 0.74 mL QuantificationHemolysis Limit or Less Ex. 23 58.63 nm 0.4 μm 60 kPa 0.79 mLQuantification Limit or Less Ex. 24 58.64 nm 0.4 μm 60 kPa 0.76 mLQuantification Limit or Less*Quantification limit of fibrinogen: 10 mg/dL

INDUSTRIAL APPLICABILITY

In the plasma or serum separation membrane according to the presentinvention, since a plurality of through holes that penetrate from oneside to the other side of the membrane are provided, it is possible toseparate plasma or serum from blood readily and securely without causinghemolysis of erythrocytes. In particular, even when a pressure of 60 kPaor less is applied, it is possible to A securely separate plasma orserum without causing breakage of erythrocytes. Therefore, it ispossible to improve the efficiency of separation of plasma or serum.

Since the filter apparatus according to the present invention has afilter member through which plasma moves faster provided in the previousstage of the plasma or serum separation membrane configured according tothe present invention, plasma dominantly moves quickly toward the plasmaor serum separation membrane from blood, so that efficiency ofseparation is further improved. Additionally, even when a whole bloodsample having high hematocrit value is used, plasma can be securely andrapidly separated because the plasma moves quickly through the filtermember.

In addition, since the need of centrifugal separation is eliminated, itis possible to rapidly obtain a specimen by using a plasma or serumseparation membrane or a filter apparatus of the present invention.Therefore, the present invention is especially useful in emergent cases.

1. A membrane for separating plasma or serum from blood, having aporosity of not more than 30%.
 2. The plasma or serum separatingmembrane according to claim 1, wherein a plurality of through holes areprovided so as to penetrate from one side to the other side of themembrane.
 3. The plasma or serum separating membrane according to claim2, wherein diameters of the through holes fall within the range of 0.05to 2.0 μm.
 4. The plasma or serum separating membrane according to claim1, wherein mean surface roughness of the membrane is not more than 100nm.
 5. The plasma or serum separating membrane according to claim 1,used as a corpuscle blocking membrane for preventing contamination bycorpuscles. 6-17. (canceled)
 18. The plasma or serum separating membraneaccording to claim 2, wherein mean surface roughness of the membrane isnot more than 100 nm.
 19. The plasma or serum separating membraneaccording to claim 3, wherein mean surface roughness of the membrane isnot more than 100 nm.
 20. The plasma or serum separating membraneaccording to claim 2, used as a corpuscle blocking membrane forpreventing contamination by corpuscles.
 21. The plasma or serumseparating membrane according to claim 3, used as a corpuscle blockingmembrane for preventing contamination by corpuscles.
 22. The plasma orserum separating membrane according to claim 4, used as a corpuscleblocking membrane for preventing contamination by corpuscles.